Production of alkali-metal carbonates



PM... Feb. 19,1929.

UNITED STATES PATENT OFFICE.

LINN BRADLEY, OF HONTOLAIB, NEW JERSEY, AND EDWARD P. 01' nw YORK, N. Y., ABBIGNOBS TO BRADLEY-loam CORPORATION, O! m YORK, I. 1.,

A CORPORATION OF NEW YORK.

PBOD'O'CTION OF ALKALI-IETLL CABBOHATBB.

No Drawing. Application fled November 5, 1921, Serial Io, 513,161. Renewed Kay 80, 1837.

This invention relates to improvements in the production of alkali-metal carbonates, and it includes an improved method of-producing alkali-metal carbonates from alkalimetal sulfites as well as from certain products resulting from the treatment of alkali-metal sulfites.

The invention is based upon the discovery that when an aqueous solution of normal sodium sulfite (Na SO is heated with cellulose-bearing materials, for example such as wood, for the production of pulp from the wood, there is produced a liquor which, upon evaporation and incineration, will under certain conditions yield a product which contains the greater part of the sodium of the original sodium sulfite, in the form of sodium carbonate.

The invention will be further illustrated by the following more detailed description, but it is intended and will be understood that the invention is illustrated by but is not limited to the specific examples thus described.

An aqueous solution of normal sodium sulfite (Na so is cooked or digested with chipped wood, for example, poplar, birch or spruce wood or other coniferous or deciduous wood, using about 30%40% or even larger amounts of the sodium sulfite (Na SO based on the air-dried weight of the wood, and using a sufficient amount of water so that the wood chips are covered by the sodium sulfite solution. The digestion may be car ried out by heating the liquor and chips by means of direct steam at a steam pressure varying from about 110 to 140 pounds (although lower or higher pressures may be used), and the digestion can be continued for a suitable period of time, for example, from ten to three hours, depending upon the wood, temperature and other factors, as will be understood by those familiar with the art, or until the wood fibres are substantially freed from non-fibrous constituents. As a result of the digestion above described, the cellulosic material itself is converted into a high grade pulp suitable for paper manufacture, etc. which is thus produced as one of the valuable products of the complete process.

The residual liquors produced by the digestion above described will contain large amounts of organic compounds, a greater or less portion of which may be sodium-organic compounds or sodium-sulfo-organic compoimds. The liquor may also contain unchanged sodium sulfite as well as other products. These liquors have a characteristic composition and they seem to contain considerable amounts of organic acids or readily oxidizable compounds, which, on oxidation, yield organic acids. These organic acids or acid compounds, when the liquor is concentrated and evaporated to dryness and incinerated in the presence of air, seem to react upon the sodium sulfite of the solution and other sulfur-containing com unds so that the greater part of the sulfur dioxide of the sodium sulfite initially employed is set free and driven off, especially when the evaporation, drying and incineration operation is conducted in the usual rotary furnace commonly used in the soda process.

The evaporation of the solution may be carried out in different ways. The solution may, for example, be evaporated in a multiple eflect evaporator until it has a specific gravity of about 40-60 Tw. and the concent-rated liquor then fed intoarota furnace such as is commonly used in the cination and incineration of concentrated black liquor produced by the s da pulp process. The rotary furnace may be heated, for example, by means of a coal fire at the lower end, that is, at the discharge end, and the hot gases from the furnace may be utilized for heating or the generation of steam in a boiler. The furnace gases in such a furnace so heated will contain nitrogen and oxygen and will promote the removal of sulfur compounds from the material undergoing incineration.

The product resulting from the evaporation and incinerating operation may contain the greater part of the sodium of the original sodium sulfite as sodium carbonate, and the sodium carbonate can be recovered, for example, by leaching with water and by concentration of the resulting solution, the solution being treated or purified by any usual means.

While we do not desire to limit ourselves by any theoretical explanation of the action which takes place in the process of the present invention, nevertheless we believe that, the action of the sodium sulfite upon the non-' cellulose constituents of the wood results in the production of complex products, includwill at the same time bonate. The sodium carbonate thus pro-v duced may, however, be admixed with varying amounts of other sodium salts, and including even sulfur-containing sodium compounds.

The sodium carbonate thus produced may be obtained in a solid state and may be further purified if desired. 7

By carrying out the calcination or destructive distillation of the dry product (resulting from evaporation) in apparatus provided with means for condensing and recovering volatilized products, such products can be recovered as valuable by-products of the process.

It will thus be seen that the process of the present invention results in the production of an alkali-metal carbonate, such as sodium carbonate, from an alkali-metal sulfite such as sodium sulfite, by treating a solution of the sulfite with cellulosic material such as wood, and by evaporation of the resulting solution and incineration of the dried product. From another standpoint, the present invention may be ccmsidered as an improvement in the treatment of residual liquors from the manufacture of pulp by the cooking of the cellulose-bearing material with a solution of alkali-metal sulfite. That is, the invention may be considered as a method of producing sodium carbonate from such residual liquors of the pulp-making process. Accordingly, we claim the invention both for the production of alkali-metal carbonate from such residual liquors, an as a complete process starting with the alkali-metal sulfite itself and by treating such sulfite in a manner which will give a product from which alkali metal carbonate can be produced, and which ive a good yield of valuable pulp as one o? the products of the complete process.

Instead of using sodiumsulfite in the manner' above described, potassium sulfite, or a mixture of sodium and potassium sulfites, can be similarly used.

We claim 1. The rocess of producing an alkalimetal car nate from an alkali-metal sulfite which comprises digesting a solution of normal alkali-metal sulfite with cellulosebearing materials, separating the resulting liquor from the cellulosic materials and treating theresulting liquor for the production of alkali-metal carbonate therefrom, by evaporating the liquor and furnacing the residue in the presence of a current of hot gases including nitrogen and oxygen and under conditions to driv off a sulfur compound and give a furnace product containin the greater part of the sodlum of the origins, sodium sulfite in the form of sodium carbonate.

2. The process of producing an alkalimetal carbonate from an alkali-metal sulfite which comprises digesting a solution of normal alkali-metal sulfite wit-h wood, separating the resulting liquor from the cellulosic materials, evaporating the resulting liquor and calcining the resulting dry product.

3. The method of producing an alkalimetal carbonate from the residual liquor resulting from the COOkiIlg of resinous wood with a solution of normal alkali-metal sulfite which comprises evaporating such liquor to dryness and calcining the dry product.

4. The process of producing sodium carbonate from sodium sulphite, which comprises digesting wood with a solution of sodium sulphite, separating the resulting liquor from the cellulosic material, concentrating the resulting liquor, subjecting the concentrated liquor to calcination, and dissolving the sodium carbonate from the calcined product.

5. The method of producing sodium carbonate from the residual liquor resulting from the cooking of wood with a solution of sodium sulphite, which comprises evaporating such liquor to dryness and calcining the dry products under oxidizing conditions, whereby the sodium compounds of the residual liquor are lar ely oxidized and converted into sodiumcar nate, and extracting the sodium carbonate from the calcined product.

6. The processof producin sodium carbonate from normal sodium su fite, which comprises digesting wood with a solution containing normal sodium sulfite amountingto at least 30% of the air-dried weight of the wood under and subjecting it to calcination therein under conditions to give a calcined product containmg the greater part of the sodium of the original sodium sulfite in the form of sodium carbonate and leaching the sodium carbonate from the calcined product.

- 8. The process of producing sodium carbonate from normal sodium sulfite, which comprises digesting Wood with a solution containing at least 30% of sodium sulfite on the air-dried weight of the wood, separating the resulting liquor at the end of the digesting operation, subjecting the same to concentration and calcination under conditions to give a calcined product containing the greater part of the sodium of the original sodium sulfite in the form of sodium carbonate, and leaching the sodium carbonate from the calcined product.

9. The method of producing sodium carbonate and of recovering sulfur dioxide from the residual liquor resulting from the cooking of Wood with a solution containing sodium monosulfite, which comprises evaporating such liquor and calcining the evaporated product under conditions to produce sulfur dioxide and to give a. calcined product containing the greater part of the sodium of the original sodium sulfite in the form of sodium carbonate, and condensing and recovering volatilized products given off during the calcination.

10. The method of producing sodium carbonate from the residual liquor resulting from the cooking of wood with a solution containing normal sodium sulfite, which comprises evaporating such liquor, feeding the evaporated product into a rotary calcining furnace and subjecting it to calcination therein under oxidizing conditions to give a calcined product containing the greater part of the sodium of the original sodium sulfite in the form of sodium carbonate, sulfur dioxide being produced during the process, and leaching the sodium carbonate admixed with varying amounts of other sodium salts from the calcined product.

11. The process of deriving a carbonate of sodium from sodium monosulfite, which comprises digesting Wood with a cooking liquor supplied with sodium monosulfite until a substantial portion of the sodium content of such sulfite is present in the form of sodium organic compounds, separatitng the resulting residual liquor from the resulting fibrous material, removing water from such residual liquor and furnacing the residue todecom: ose such sodium-organic compounds and burn organic matter and recovering sodium compounds including sodium carbonate.

12. The process of producing an alkali-metal carbonate from sodium monosulfite, which comprises digesting cellulose-bearing material by means of cooking liquor supplied with sodium monosulfite and continuing the digesting treatment until non-fibrous organic constituents of such cellulose-bearing material have been so digested as to render fibres thereof readily'separable from each other by mechanical treatment and thereby form such a residual liquor as, upon evaporation and incineration in a rotary furnace in such manner as is customarily employed in working up black liquor produced from wood by the conventional soda process, is capable of forming furnace gases which carry a preponderating amount of the sulfur combined with sodium monosulfite when supplied to such a cooking liquor, separating such residual liquor from the resulting fibrous material, removing Water from such residual liquor and incinerating the resulting residue under conditions adapted to form furnace gases which carry such a preponderating amount of such sulfur and thus form a furnace product including an alkali-metal carbonate, substantially all of the salts contained in the furnace product being soluble in water.

1.3. The process of producing a carbonate of sodium from a sulfite of sodium, which comprises digesting wood by means of cooking liquor supplied with about 30% to 40% of sodium monosulfite (N a SO based on the air-dried weight of the'wood and continuing the digesting treatment until there is produced such a residual liquor as, upon evaporation and incineration in a rotary furnace in such manner as is customarily employed in working up black liquor produced from wood by the conventional soda process, is capable of forming a furnace product including sodium carbonate, separating such residual liquor from the resulting fibrous material, removing water from such residual liquor and incinerating the resulting residue under conditions adapted to form a furnace product including sodium carbonate and under conditions to form furnace gases which carry sulfur-bearing material derived from such residual liquor to such an extent that the greater part of the alkali-metal content of the sodium monosulfite supplied to the cooking liquor is present in the furnace product as sodium carbonate, and substantially all of the salts contained in the furnace product being readily soluble in water.

14. The process of deriving a carbonate of sodium from sodium monosulfite, which comprises digesting wood by means of cooking liquor supplied with sodium monosulfite and continuing the digesting treatment until there is produced such a residual liquor as, upon evaporation and calcination in a rotary furnace in such manner as is customarily employed in working up black liquor produced by digesting wood by the usual caustic soda cooking liquor of the conventional soda process, is capable of yielding a furnace product including sodium carbonate and sodium-sulfur compounds, "the sodium content of the'former being in excess of the sodium content of the latter,.and then separating such residual liquor from the resulting i fibrous material, removing water from such residual liquor and calcining the residue under conditions adapted to form such a furnace product and to form furnace gases which carry sulfur-bearing material derived from constituents of such residual liquor to an extent sufficient to prevent the furnace product carrying more sodium content as sodium-sulfur compounds than as sodium carbonate, and substantially all of the sulfurcompounds in such furnace product being readily soluble in water, and subsequently forming a solution including sodium-sulfur compounds derived from such furnace product and also including a carbonate of sodium.

15. In a process for deriving a carbonate of sodium and a sodium-sulfur compound from sodium monosulfite, the steps which comprise digesting Wood by means of cooking liquor supplied with at least about 30% of sodium monosulfite (Na SO based on the air-dried weight of the wood, and continuing the digesting treatment until substantially all of the readily digestible non-fibrous organic matter thereof has been digested and there is produced such a residual liquor as, upon evaporation and calcination in a rotary furnace in such manner as is customarily employed in working up black liquor produced by digesting wood by the usual caustic soda cooking liquor of the conventional soda proc ess, is capable of yielding a furnace product containing in the form of sodium carbonate the greater part of the sodium of the,sodium monosulfite and also containing sodium-sulfur compounds, and then separating such residual liquor from the resulting fibrous material, removing Water from such residual liquor and calcining the residue under conditions adapted to form such a furnace product, and subsequently forming a solution including substantially all of the sodium and sulfur compounds contained in such furnace product.

16. The process of producing sodium carbonate from sodium sulfite which comprises digesting a solution of normal sodium sulfite with resinous wood, the solution containing about 30% to 40% of the sodium sulfite based on the air-dried weight of the wood, and continuing the digestion until the wood fibres are substantially freed from non-fibrous constit uents, separating the resulting liquor from the cellulosic materials, evaporating the resulting liquor and calcining the resulting dry product.

In witness whereof we have hereunto aflixed our signatures.

LINN BRADLEY. EDWARD P. MCKEEFE. 

